/* * linux/arch/x86_64/kernel/head.S -- start in 32bit and switch to 64bit * * Copyright (C) 2000 Andrea Arcangeli SuSE * Copyright (C) 2000 Pavel Machek * Copyright (C) 2000 Karsten Keil * Copyright (C) 2001,2002 Andi Kleen * Copyright (C) 2005 Eric Biederman */ #include #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_PARAVIRT #include #include #define GET_CR2_INTO(reg) GET_CR2_INTO_RAX ; movq %rax, reg #else #define GET_CR2_INTO(reg) movq %cr2, reg #define INTERRUPT_RETURN iretq #endif /* we are not able to switch in one step to the final KERNEL ADDRESS SPACE * because we need identity-mapped pages. * */ #define pud_index(x) (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1)) L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET) L3_PAGE_OFFSET = pud_index(__PAGE_OFFSET) L4_START_KERNEL = pgd_index(__START_KERNEL_map) L3_START_KERNEL = pud_index(__START_KERNEL_map) .text __HEAD .code64 .globl startup_64 startup_64: /* * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1, * and someone has loaded an identity mapped page table * for us. These identity mapped page tables map all of the * kernel pages and possibly all of memory. * * %esi holds a physical pointer to real_mode_data. * * We come here either directly from a 64bit bootloader, or from * arch/x86_64/boot/compressed/head.S. * * We only come here initially at boot nothing else comes here. * * Since we may be loaded at an address different from what we were * compiled to run at we first fixup the physical addresses in our page * tables and then reload them. */ /* Compute the delta between the address I am compiled to run at and the * address I am actually running at. */ leaq _text(%rip), %rbp subq $_text - __START_KERNEL_map, %rbp /* Is the address not 2M aligned? */ movq %rbp, %rax andl $~PMD_PAGE_MASK, %eax testl %eax, %eax jnz bad_address /* Is the address too large? */ leaq _text(%rip), %rdx movq $PGDIR_SIZE, %rax cmpq %rax, %rdx jae bad_address /* Fixup the physical addresses in the page table */ addq %rbp, init_level4_pgt + 0(%rip) addq %rbp, init_level4_pgt + (L4_PAGE_OFFSET*8)(%rip) addq %rbp, init_level4_pgt + (L4_START_KERNEL*8)(%rip) addq %rbp, level3_ident_pgt + 0(%rip) addq %rbp, level3_kernel_pgt + (510*8)(%rip) addq %rbp, level3_kernel_pgt + (511*8)(%rip) addq %rbp, level2_fixmap_pgt + (506*8)(%rip) /* Add an Identity mapping if I am above 1G */ leaq _text(%rip), %rdi andq $PMD_PAGE_MASK, %rdi movq %rdi, %rax shrq $PUD_SHIFT, %rax andq $(PTRS_PER_PUD - 1), %rax jz ident_complete leaq (level2_spare_pgt - __START_KERNEL_map + _KERNPG_TABLE)(%rbp), %rdx leaq level3_ident_pgt(%rip), %rbx movq %rdx, 0(%rbx, %rax, 8) movq %rdi, %rax shrq $PMD_SHIFT, %rax andq $(PTRS_PER_PMD - 1), %rax leaq __PAGE_KERNEL_IDENT_LARGE_EXEC(%rdi), %rdx leaq level2_spare_pgt(%rip), %rbx movq %rdx, 0(%rbx, %rax, 8) ident_complete: /* * Fixup the kernel text+data virtual addresses. Note that * we might write invalid pmds, when the kernel is relocated * cleanup_highmap() fixes this up along with the mappings * beyond _end. */ leaq level2_kernel_pgt(%rip), %rdi leaq 4096(%rdi), %r8 /* See if it is a valid page table entry */ 1: testq $1, 0(%rdi) jz 2f addq %rbp, 0(%rdi) /* Go to the next page */ 2: addq $8, %rdi cmp %r8, %rdi jne 1b /* Fixup phys_base */ addq %rbp, phys_base(%rip) /* Due to ENTRY(), sometimes the empty space gets filled with * zeros. Better take a jmp than relying on empty space being * filled with 0x90 (nop) */ jmp secondary_startup_64 ENTRY(secondary_startup_64) /* * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1, * and someone has loaded a mapped page table. * * %esi holds a physical pointer to real_mode_data. * * We come here either from startup_64 (using physical addresses) * or from trampoline.S (using virtual addresses). * * Using virtual addresses from trampoline.S removes the need * to have any identity mapped pages in the kernel page table * after the boot processor executes this code. */ /* Enable PAE mode and PGE */ movl $(X86_CR4_PAE | X86_CR4_PGE), %eax movq %rax, %cr4 /* Setup early boot stage 4 level pagetables. */ movq $(init_level4_pgt - __START_KERNEL_map), %rax addq phys_base(%rip), %rax movq %rax, %cr3 /* Ensure I am executing from virtual addresses */ movq $1f, %rax jmp *%rax 1: /* Check if nx is implemented */ movl $0x80000001, %eax cpuid movl %edx,%edi /* Setup EFER (Extended Feature Enable Register) */ movl $MSR_EFER, %ecx rdmsr btsl $_EFER_SCE, %eax /* Enable System Call */ btl $20,%edi /* No Execute supported? */ jnc 1f btsl $_EFER_NX, %eax 1: wrmsr /* Make changes effective */ /* Setup cr0 */ #define CR0_STATE (X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \ X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \ X86_CR0_PG) movl $CR0_STATE, %eax /* Make changes effective */ movq %rax, %cr0 /* Setup a boot time stack */ movq stack_start(%rip),%rsp /* zero EFLAGS after setting rsp */ pushq $0 popfq /* * We must switch to a new descriptor in kernel space for the GDT * because soon the kernel won't have access anymore to the userspace * addresses where we're currently running on. We have to do that here * because in 32bit we couldn't load a 64bit linear address. */ lgdt early_gdt_descr(%rip) /* set up data segments */ xorl %eax,%eax movl %eax,%ds movl %eax,%ss movl %eax,%es /* * We don't really need to load %fs or %gs, but load them anyway * to kill any stale realmode selectors. This allows execution * under VT hardware. */ movl %eax,%fs movl %eax,%gs /* Set up %gs. * * The base of %gs always points to the bottom of the irqstack * union. If the stack protector canary is enabled, it is * located at %gs:40. Note that, on SMP, the boot cpu uses * init data section till per cpu areas are set up. */ movl $MSR_GS_BASE,%ecx movl initial_gs(%rip),%eax movl initial_gs+4(%rip),%edx wrmsr /* esi is pointer to real mode structure with interesting info. pass it to C */ movl %esi, %edi /* Finally jump to run C code and to be on real kernel address * Since we are running on identity-mapped space we have to jump * to the full 64bit address, this is only possible as indirect * jump. In addition we need to ensure %cs is set so we make this * a far return. */ movq initial_code(%rip),%rax pushq $0 # fake return address to stop unwinder pushq $__KERNEL_CS # set correct cs pushq %rax # target address in negative space lretq /* SMP bootup changes these two */ __REFDATA .align 8 ENTRY(initial_code) .quad x86_64_start_kernel ENTRY(initial_gs) .quad INIT_PER_CPU_VAR(irq_stack_union) ENTRY(stack_start) .quad init_thread_union+THREAD_SIZE-8 .word 0 __FINITDATA bad_address: jmp bad_address .section ".init.text","ax" .globl early_idt_handlers early_idt_handlers: # 104(%rsp) %rflags # 96(%rsp) %cs # 88(%rsp) %rip # 80(%rsp) error code i = 0 .rept NUM_EXCEPTION_VECTORS .if (EXCEPTION_ERRCODE_MASK >> i) & 1 ASM_NOP2 .else pushq $0 # Dummy error code, to make stack frame uniform .endif pushq $i # 72(%rsp) Vector number jmp early_idt_handler i = i + 1 .endr ENTRY(early_idt_handler) cld cmpl $2,early_recursion_flag(%rip) jz 1f incl early_recursion_flag(%rip) pushq %rax # 64(%rsp) pushq %rcx # 56(%rsp) pushq %rdx # 48(%rsp) pushq %rsi # 40(%rsp) pushq %rdi # 32(%rsp) pushq %r8 # 24(%rsp) pushq %r9 # 16(%rsp) pushq %r10 # 8(%rsp) pushq %r11 # 0(%rsp) cmpl $__KERNEL_CS,96(%rsp) jne 10f leaq 88(%rsp),%rdi # Pointer to %rip call early_fixup_exception andl %eax,%eax jnz 20f # Found an exception entry 10: #ifdef CONFIG_EARLY_PRINTK GET_CR2_INTO(%r9) # can clobber any volatile register if pv movl 80(%rsp),%r8d # error code movl 72(%rsp),%esi # vector number movl 96(%rsp),%edx # %cs movq 88(%rsp),%rcx # %rip xorl %eax,%eax leaq early_idt_msg(%rip),%rdi call early_printk cmpl $2,early_recursion_flag(%rip) jz 1f call dump_stack #ifdef CONFIG_KALLSYMS leaq early_idt_ripmsg(%rip),%rdi movq 40(%rsp),%rsi # %rip again call __print_symbol #endif #endif /* EARLY_PRINTK */ 1: hlt jmp 1b 20: # Exception table entry found popq %r11 popq %r10 popq %r9 popq %r8 popq %rdi popq %rsi popq %rdx popq %rcx popq %rax addq $16,%rsp # drop vector number and error code decl early_recursion_flag(%rip) INTERRUPT_RETURN .balign 4 early_recursion_flag: .long 0 #ifdef CONFIG_EARLY_PRINTK early_idt_msg: .asciz "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n" early_idt_ripmsg: .asciz "RIP %s\n" #endif /* CONFIG_EARLY_PRINTK */ .previous #define NEXT_PAGE(name) \ .balign PAGE_SIZE; \ ENTRY(name) /* Automate the creation of 1 to 1 mapping pmd entries */ #define PMDS(START, PERM, COUNT) \ i = 0 ; \ .rept (COUNT) ; \ .quad (START) + (i << PMD_SHIFT) + (PERM) ; \ i = i + 1 ; \ .endr .data /* * This default setting generates an ident mapping at address 0x100000 * and a mapping for the kernel that precisely maps virtual address * 0xffffffff80000000 to physical address 0x000000. (always using * 2Mbyte large pages provided by PAE mode) */ NEXT_PAGE(init_level4_pgt) .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE .org init_level4_pgt + L4_PAGE_OFFSET*8, 0 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE .org init_level4_pgt + L4_START_KERNEL*8, 0 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */ .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE NEXT_PAGE(level3_ident_pgt) .quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE .fill 511,8,0 NEXT_PAGE(level3_kernel_pgt) .fill L3_START_KERNEL,8,0 /* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */ .quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE .quad level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE NEXT_PAGE(level2_fixmap_pgt) .fill 506,8,0 .quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */ .fill 5,8,0 NEXT_PAGE(level1_fixmap_pgt) .fill 512,8,0 NEXT_PAGE(level2_ident_pgt) /* Since I easily can, map the first 1G. * Don't set NX because code runs from these pages. */ PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD) NEXT_PAGE(level2_kernel_pgt) /* * 512 MB kernel mapping. We spend a full page on this pagetable * anyway. * * The kernel code+data+bss must not be bigger than that. * * (NOTE: at +512MB starts the module area, see MODULES_VADDR. * If you want to increase this then increase MODULES_VADDR * too.) */ PMDS(0, __PAGE_KERNEL_LARGE_EXEC, KERNEL_IMAGE_SIZE/PMD_SIZE) NEXT_PAGE(level2_spare_pgt) .fill 512, 8, 0 #undef PMDS #undef NEXT_PAGE .data .align 16 .globl early_gdt_descr early_gdt_descr: .word GDT_ENTRIES*8-1 early_gdt_descr_base: .quad INIT_PER_CPU_VAR(gdt_page) ENTRY(phys_base) /* This must match the first entry in level2_kernel_pgt */ .quad 0x0000000000000000 #include "../../x86/xen/xen-head.S" .section .bss, "aw", @nobits .align L1_CACHE_BYTES ENTRY(idt_table) .skip IDT_ENTRIES * 16 .align L1_CACHE_BYTES ENTRY(nmi_idt_table) .skip IDT_ENTRIES * 16 __PAGE_ALIGNED_BSS .align PAGE_SIZE ENTRY(empty_zero_page) .skip PAGE_SIZE